Invariant natural killer T (iNKT) cells are a subset of T lymphocytes that recognize glycolipid antigens presented by the MHC class l-related protein CD1d. Emerging evidence indicates that iNKT cells play a regulatory role in the immune system. The long-term goal of this proposal is to obtain a better understanding of the in vivo immune response of mice to various stimulators of iNKT cells and to utilize this information for the development of better prophylactic and therapeutic approaches of human disease. Studies from our laboratory have demonstrated that the prototypical iNKT cell antigen, alpha-galactosylceramide (GalCer) can prevent disease in experimental models of type 1 diabetes, multiple sclerosis and lupus. Despite the impact of GalCer treatment on a variety of disease processes, our understanding of the response of iNKT cells themselves to glycolipid antigens is limited. Recent studies from our laboratory have demonstrated that the response of iNKT cells to GalCer activation is characterized by surface receptor down-modulation, expansion, cytokine production, cross-talk with other cells, homeostatic contraction, and acquisition of an anergic phenotype. Guided by these preliminary findings, our proposed studies will test the overall hypothesis that glycolipid activation of iNKT cells initiates a program of anergy induction with long-term effects on subsequent iNKT cell-controlled immune responses. We will test this hypothesis in three integrated Specific Aims: Aim 1 will determine the cellular interactions that are critical for the induction and maintenance of long-term iNKT cell anergy, Aim 2 will investigate the biochemical mechanisms involved in the induction and maintenance of iNKT cell anergy, and Aim 3 will evaluate the long-term effects of iNKT cell unresponsiveness to the subsequent generation of iNKT cell-controlled immune responses. Completion of the work described in this proposal will provide novel insight into fundamental iNKT cell biology, the response of iNKT cells to glycolipid antigens, and the immunomodulatory activities of iNKT cells during health and disease. These proposed studies will build a foundation of knowledge on which safe and effective iNKT cell-based vaccines and therapies can be established. Relevance to Public Health: Studies proposed in this application will contribute significantly to the development of better preventive measures and therapies of infections, cancers, and autoimmune (e.g., type 1 diabetes, multiple sclerosis and lupus), allergic and inflammatory (e.g., atherosclerosis) diseases. [unreadable] [unreadable] [unreadable]